The present invention relates to optical systems, and, more particularly, to an optical novelty filter.
A novelty filter recognizes what is new or different in one pattern compared with a set of one or more reference patterns. A "tracking" novelty filter continually updates a reference pattern in time. Thus, the device extracts changes which occur in a pattern from one time frame to the next.
Tracking novelty filters have been employed at least since the early days of radar when they were used to keep radar screens from becoming cluttered by nonmoving objects. This kind of filter is easily implemented with a digital computer by subtracting incoming images, pixel-by-pixel, from a stored reference image and periodically updating the reference image.
A disadvantage of the digital subtraction approach is that updates are limited by processing and accessing rates. As a corollary, imaging speed decreases in proportion to the number of pixels. Thus, scaling to high resolution images reduces the processing
In addition, a digital system requires a great many components resulting in considerable bulk and expense. Furthermore, the large number of components increases the number of possible error sources, thus decreasing reliability. Despite advances in electronic technology providing for greater integration of components and reduction of size, the number of components required for some applications remains problematic.
What is needed is an alternative novelty filter which can be scaled readily to any resolution and is not significantly limited by processing speed. Futhermore, such a novelty filter should comprise relatively few components for decreased cost and improved reliability.